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authorZachary Amsden <zach@vmware.com>2007-03-05 03:30:35 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-05 10:57:52 -0500
commit6cb9a8350aee789100a365794272ed20cc8f2401 (patch)
treec2e319b30ebcb6c9d247382303f7fcff1ab0d641 /include/asm-i386/time.h
parent7507ba34e827ca3c6bbcd34d20a8df8ba365fca6 (diff)
[PATCH] vmi: sched clock paravirt op fix
The custom_sched_clock hook is broken. The result from sched_clock needs to be in nanoseconds, not in CPU cycles. The TSC is insufficient for this purpose, because TSC is poorly defined in a virtual environment, and mostly represents real world time instead of scheduled process time (which can be interrupted without notice when a virtual machine is descheduled). To make the scheduler consistent, we must expose a different nature of time, that is scheduled time. So deprecate this custom_sched_clock hack and turn it into a paravirt-op, as it should have been all along. This allows the tsc.c code which converts cycles to nanoseconds to be shared by all paravirt-ops backends. It is unfortunate to add a new paravirt-op, but this is a very distinct abstraction which is clearly different for all virtual machine implementations, and it gets rid of an ugly indirect function which I ashamedly admit I hacked in to try to get this to work earlier, and then even got in the wrong units. Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/asm-i386/time.h')
-rw-r--r--include/asm-i386/time.h1
1 files changed, 0 insertions, 1 deletions
diff --git a/include/asm-i386/time.h b/include/asm-i386/time.h
index 571b4294dc2e..ea8065af825a 100644
--- a/include/asm-i386/time.h
+++ b/include/asm-i386/time.h
@@ -30,7 +30,6 @@ static inline int native_set_wallclock(unsigned long nowtime)
30 30
31#ifdef CONFIG_PARAVIRT 31#ifdef CONFIG_PARAVIRT
32#include <asm/paravirt.h> 32#include <asm/paravirt.h>
33extern unsigned long long native_sched_clock(void);
34#else /* !CONFIG_PARAVIRT */ 33#else /* !CONFIG_PARAVIRT */
35 34
36#define get_wallclock() native_get_wallclock() 35#define get_wallclock() native_get_wallclock()